Review request 12k vs 11k on 9x9

Hi,

I’d really like to see a review of https://online-go.com/game/1924559

I really had no idea of who would win during the game and because we waited so long before playing contact moves, I can’t really tell what could’ve happened. C4 feels like it’s a mistake though but I don’t really know what else I could’ve done to secure that corner.

Thank you in advance for your help.